sixth chord as I chord

I thought this one was easy ..I still have this question unsolved. any feedback? thanks a lot.

Nothing helpful from me, I'm afraid. I don't think I've ever seen a major scale where every note is harmonised as a 7th chord except for the tonic which is a sixth.

I'm at a loss too. I vaguely remember seeing something like that once, but I can't remember where... no examples of it in any of the books I have here, or any harmonized scale examples I found online.

This is an excerpt from Arnie Berle's 'Patterns Scales & Modes ofr Jazz Guitar' :
'The following rules apply to all major scales:
The I and IV are major seventh chords (the I chord is also a major sixth).
The II,III and VI are minor seventh chords.
The V is a dominant seventh chord.
The VII is a half diminished, also refered as minor seventth flat five.
....
I maj7 (I6) Establishes the key.Offers a feeling of rest or completion.All other chords tend to move to the I chord.'

I bought this book this year, but I kept this question from other sources that i read before. I'm sorry I didn't find other texts now referring to this subject (maybe I exaggerated saying that many books include this). thanks.

(EDIT) Wait a second! I found this paragraph in William Leavitt's Modern Method for Guitar 2. p71 :
'Theory: Diatonic 7th chords ......Because of a conflict with the root in the melody, the four part structures used in the I and IV are often 6th chords built from major scale degrees 1,3,5 and 6.You might say this is a result of the substitution of VIm7 over the root of the I chord and IIm7 over the root of the IV chord: am7 = C6. Dm7= F6.'
Maybe this brought a bit of light to this thread.

I don't have that book, but I was able to see that page on Amazon's "look inside the book" feature.

The I6 can stand in for the Imaj7. He shows both - the Imaj7 first, then the I6 in parenthesis.

"Notice in the harmonized scale below the first chord shown is a major seventh, but it is also shown as a major sixth chord. The major sixth is formed by taking the first, third, fifth, and sixth notes of the major scale. It is used either with or in place of the major seventh chord."

The I6 is actually enharmonic to the relative minor seventh... C-E-G-A = A-C-E-G. You can use it in place of the major 7th, just as you can use a minor chord in place of its relative major. Using the I6 usually won't give you as strong a sense of key as the Imaj7, but it can be freely used as a substitution - they share three tones.

Does that help?

Of course it helps Tom..thanks a lot!
Before I go what do you think about that William Leaviit's comment? (I'm copying it again):
'......Because of a conflict with the root in the melody, the four part structures used in the I and IV are often 6th chords built from major scale degrees 1,3,5 and 6.' what does he mean about the conflict with the root in the melody?

He means most melodies end on the 1 of the scale, and the maj7 chord has a 7 - together, they can make a minor second interval, which is a fairly strong dissonance; this is the same reason major 11th chords usually don't include the third - there's a minor second interval between the 3rd and 11th/4th.

In a theory sense, it has nothing to do with how you harmonize a major scale. In a practical sense he's right... but using a substitution for the major 7th is only one solution to the problem. There are plenty of others:

1. Don't end the melody on the tonic. Although this isn't common (and it's strictly forbidden in traditional counterpoint), there are compositions that end on the fifth.

2. Let the melody rise from the 7th to the root. This is VERY common. And even though the chart will just say Cmaj7 for a B-C transition at the end, anybody in the band playing the B note will probably rise with it, giving you a major triad for all practical purposes.

3. End on a different chord. The 6th is one possibility - but the 6/9 is also common. You'll also see tunes - even jazz tunes - that end on a major triad. I don't think of these as substitutions, though... they're choices the composer made.

4. Pay attention to the voices. Music theory is really about what's on the page; theory reduces all intervals to an octave or less for analysis. In practice, how you voice something adds a great deal to its perceived consonance or dissonance, and this is something that can't be reduced to universal rules (because our perception of what's dissonant or consonant depends in large part on memory, and rules simply can't take into account everything that you might have just heard in a piece).

To illustrate the importance of voice leading, here's an example. The V-I progression is played three times:

G7 -> Cmaj7, badly voiced (closed chords, second inversion G7 to third inversion Cmaj7)... pretty dissonant

G7 -> C, voiced as a perfect authentic cadence... very consonant

G7 -> Cmaj7 with a better voicing (open chords*, second inversion G7 to root position Cmaj7, outer voices in contrary motion, the B note oblique in the alto voice with wide spacing - it's a perfect fifth above the tenor, and a minor sixth below the soprano)... it's not as consonant as the PAC, but it's much better than the bad voicing.

*For the passersby - "open chords" in music theory means the voices are widely spaced - they're not the same as "open chords" on the guitar. Open chords on the guitar are usually open chords in music theory, but so are the typical barre chords.

Perfect!!! 'nuff said.

all the best
Roberto